From 7fa58427832e5dfaa6f9743650be7df15645a414 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Tue, 1 Mar 2022 18:30:55 +0900
Subject: [PATCH 1/2] Add global statistics output for all realm reads/writes

---
 osu.Game/Database/RealmAccess.cs | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/osu.Game/Database/RealmAccess.cs b/osu.Game/Database/RealmAccess.cs
index 9bdbebfe89..f63e858b6f 100644
--- a/osu.Game/Database/RealmAccess.cs
+++ b/osu.Game/Database/RealmAccess.cs
@@ -14,14 +14,14 @@ using osu.Framework.Input.Bindings;
 using osu.Framework.Logging;
 using osu.Framework.Platform;
 using osu.Framework.Statistics;
-using osu.Game.Configuration;
 using osu.Game.Beatmaps;
+using osu.Game.Configuration;
 using osu.Game.Input.Bindings;
 using osu.Game.Models;
-using osu.Game.Skinning;
-using osu.Game.Stores;
 using osu.Game.Rulesets;
 using osu.Game.Scoring;
+using osu.Game.Skinning;
+using osu.Game.Stores;
 using Realms;
 using Realms.Exceptions;
 
@@ -85,6 +85,14 @@ namespace osu.Game.Database
 
         private static readonly GlobalStatistic<int> total_subscriptions = GlobalStatistics.Get<int>(@"Realm", @"Subscriptions");
 
+        private static readonly GlobalStatistic<int> total_reads_update = GlobalStatistics.Get<int>(@"Realm", @"Reads (Update)");
+
+        private static readonly GlobalStatistic<int> total_reads_async = GlobalStatistics.Get<int>(@"Realm", @"Reads (Async)");
+
+        private static readonly GlobalStatistic<int> total_writes_update = GlobalStatistics.Get<int>(@"Realm", @"Writes (Update)");
+
+        private static readonly GlobalStatistic<int> total_writes_async = GlobalStatistics.Get<int>(@"Realm", @"Writes (Async)");
+
         private readonly object realmLock = new object();
 
         private Realm? updateRealm;
@@ -213,8 +221,12 @@ namespace osu.Game.Database
         public T Run<T>(Func<Realm, T> action)
         {
             if (ThreadSafety.IsUpdateThread)
+            {
+                total_reads_update.Value++;
                 return action(Realm);
+            }
 
+            total_reads_async.Value++;
             using (var realm = getRealmInstance())
                 return action(realm);
         }
@@ -226,9 +238,13 @@ namespace osu.Game.Database
         public void Run(Action<Realm> action)
         {
             if (ThreadSafety.IsUpdateThread)
+            {
+                total_reads_update.Value++;
                 action(Realm);
+            }
             else
             {
+                total_reads_async.Value++;
                 using (var realm = getRealmInstance())
                     action(realm);
             }
@@ -241,9 +257,14 @@ namespace osu.Game.Database
         public void Write(Action<Realm> action)
         {
             if (ThreadSafety.IsUpdateThread)
+            {
+                total_writes_update.Value++;
                 Realm.Write(action);
+            }
             else
             {
+                total_writes_async.Value++;
+
                 using (var realm = getRealmInstance())
                     realm.Write(action);
             }

From 9a117467b5ea36389da063102c051ce7eef86ed2 Mon Sep 17 00:00:00 2001
From: Dean Herbert <pe@ppy.sh>
Date: Tue, 1 Mar 2022 18:31:33 +0900
Subject: [PATCH 2/2] Add `RealmAccess.WriteAsync` method

---
 .../RealmSubscriptionRegistrationTests.cs     | 29 +++++++++++++++++++
 osu.Game/Database/RealmAccess.cs              | 12 ++++++++
 2 files changed, 41 insertions(+)

diff --git a/osu.Game.Tests/Database/RealmSubscriptionRegistrationTests.cs b/osu.Game.Tests/Database/RealmSubscriptionRegistrationTests.cs
index d62ce3b585..02d617d0e0 100644
--- a/osu.Game.Tests/Database/RealmSubscriptionRegistrationTests.cs
+++ b/osu.Game.Tests/Database/RealmSubscriptionRegistrationTests.cs
@@ -4,8 +4,10 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading.Tasks;
 using NUnit.Framework;
 using osu.Framework.Allocation;
+using osu.Framework.Extensions;
 using osu.Game.Beatmaps;
 using osu.Game.Rulesets;
 using osu.Game.Tests.Resources;
@@ -18,6 +20,33 @@ namespace osu.Game.Tests.Database
     [TestFixture]
     public class RealmSubscriptionRegistrationTests : RealmTest
     {
+        [Test]
+        public void TestSubscriptionWithAsyncWrite()
+        {
+            ChangeSet? lastChanges = null;
+
+            RunTestWithRealm((realm, _) =>
+            {
+                var registration = realm.RegisterForNotifications(r => r.All<BeatmapSetInfo>(), onChanged);
+
+                realm.Run(r => r.Refresh());
+
+                // Without forcing the write onto its own thread, realm will internally run the operation synchronously, which can cause a deadlock with `WaitSafely`.
+                Task.Run(async () =>
+                {
+                    await realm.WriteAsync(r => r.Add(TestResources.CreateTestBeatmapSetInfo()));
+                }).WaitSafely();
+
+                realm.Run(r => r.Refresh());
+
+                Assert.That(lastChanges?.InsertedIndices, Has.One.Items);
+
+                registration.Dispose();
+            });
+
+            void onChanged(IRealmCollection<BeatmapSetInfo> sender, ChangeSet? changes, Exception error) => lastChanges = changes;
+        }
+
         [Test]
         public void TestSubscriptionWithContextLoss()
         {
diff --git a/osu.Game/Database/RealmAccess.cs b/osu.Game/Database/RealmAccess.cs
index f63e858b6f..bf2b48ea52 100644
--- a/osu.Game/Database/RealmAccess.cs
+++ b/osu.Game/Database/RealmAccess.cs
@@ -8,6 +8,7 @@ using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Threading;
+using System.Threading.Tasks;
 using osu.Framework.Allocation;
 using osu.Framework.Development;
 using osu.Framework.Input.Bindings;
@@ -270,6 +271,17 @@ namespace osu.Game.Database
             }
         }
 
+        /// <summary>
+        /// Write changes to realm asynchronously, guaranteeing order of execution.
+        /// </summary>
+        /// <param name="action">The work to run.</param>
+        public async Task WriteAsync(Action<Realm> action)
+        {
+            total_writes_async.Value++;
+            using (var realm = getRealmInstance())
+                await realm.WriteAsync(action);
+        }
+
         /// <summary>
         /// Subscribe to a realm collection and begin watching for asynchronous changes.
         /// </summary>